Diverse type dipole antennas on common mount

ABSTRACT

An antenna means comprising a linear element of a conductor having a length sufficiently shorter than a half wavelength and a plurality of parallel two-wire type distributed constants transmission lines short-circuited at the free end thereof, said transmission lines being sequentially arranged along the linear conductor element and connected to the same element, whereby compensation of the impedance characteristics of the antenna is achieved without decreasing the antenna efficiency.

United States Paten [191 Fujimoto et a1.

154] DIVERSE TYPE DIPOLE ANTENNAS ON COMMON MOUNT [75] Inventors! KyoheiFujimoto, Fujisawa;

Nobuyuki Suyama, Chigasaki; Yoshiyasu Hiroi, Yokohama; Hideo Ito,Yokohama; Hiroshi Haruki, Yokohama; Takao Ogawa, Yokohama; TsutomuKobayashi, Kadoma, all of Japan [7.3] Assignee: Matsushita ElectricIndustrial Co.,

Ltd., Osaka, Japan [22] Filed: June 12, 1972 [21] Appl. No.: 261,973

I [30] Foreign Application Priority Data June 14, 1971 Japan... 46-50485June 14, 1971 Japan.... 46-50484 June 14, 1971 Japan 46-50487 [52] U.S.Cl. 343/794, 343/802 [51] Int. Cl. H011] 9/16 [58] Field of Search343/802, 806, 828, 794

[4 1 Apr. 16, 1974 [56] References Cited UNITED STATES PATENTS 3,231,8941/1966 Nagai .f. 343/806 3,689,929 9/1972 Moody 343/802 2,682,608 6/1954Johnson..... 343/802 2,380,333 7/1945 Scheldorf.... 343/802 1,987,7801/1935 Latour 343/806 3,61 1.397 10/1971 Poliakoff.... 343/802 PrimaryExaminer-Eli Lieberman Attorney, Agent, or Firm-Stevens, Davis, Miller &Mosher [57] ABSTRACT An antenna means comprising a linear element of aconductor having a length sufficiently shorter than a half wavelengthand a plurality of parallel two-wire type distributed constantstransmission lines shortcircuited at the free end thereof, saidtransmission lines being sequentially arranged along the linearconductor element and connected to the same element, wherebycompensation of the impedance characteristics of the antenna is achievedwithout decreasing the antenna efficiency.

1 Claim, 14 Drawing Figures ATENTEUAPR 16 um SHEET 1 OF 4 FIG. 2

ATENTEDAPRIS W V I 3.805269 SHEEI 2 0F 4 NURMAL/ZED WPEDANCE 500 UAPR 161974 3805.269

SHEET u or 4 FIG. /0b

This invention relates to an antenna means of comparatively small size,particularly to such a means designed to have well compensated impedancecharacteristics and yet to maintain good antenna efficiency.

Generally, small linear antennas the length of which is sufficientlyshorter than a half wavelength, have an impedance characteristics inwhich the resistive component is comparatively small and the capacitivecomponent iis comparatively large. Therefore, the mismatch loss with areceiver is accordingly large.

Hitherto, in order to compensate such an impedance characteristic, aninductance of concentrated constants (or a coil) has been attached tothe antenna at the intermediate portion or at the driving terminalsthereof. Such a loading has caused a decrease in the antenna efficiencydue to a loss in the inductance (coil). Further, the radiation impedanceof the antenna is usually small.

An object of this invention is to remove the abovementioned drawbacks ofa small antenna by loading it with inductances of distributed constants.

Another object of this invention is to provide a small antenna which hasa long life and can be easily handled.

A further object of this invention is to provide a small antenna whichcan be easily formed as a composite antenna.

In order to achieve the above objects, the antenna of this inventioncomprises an aligned series of linear conductors the total length ofwhich is substantially shorter than a half wavelength in the operatingfrequency band and a pluralityof parallel two-wire type distributedconstants transmission lines short-circuited at one end thereof, saidtransmission lines being connected between two adjacent conductors ofsaid series of linear conductorsat the other end thereof.

This invention will be described in detail with reference to theaccompanying drawings, in which:

FIG. 1 is a diagram of a fundamental two-wire distributed constantstransmission line;

FIGS. 2, 3, 4 and 5 are schematic diagrams of the antenna of thisinvention shown in various forms;

FIG. 6 is a chart showing comparison of the impedance relations betweenthe antennas of this invention and of the conventional one;

FIGS. 7, 8 and 9 are schematic diagram of modified forms of the antennaof this invention;

FIGS. 10a, 10b and 100 are views relating to a practical embodiment ofthis invention; and

FIGS. 11 and 12 are views of another embodiment of this invention.

Referring to FIG. 1 which shows a distributed constnnts transmision lineof parallel two-wire type short-circuited at the load end, the impedanceof the line at the sending end a,a' contains an inductive component Zexpressed by the following formula:

2 jW tan Bl (l) where W, is the characteristic impedance of the line, Bis the phase constant, and I is the length of the line.

FIG. 2 schematically shows anembodiment of the antenna of thisinvention, in which a plurality of shortcircuited transmission-lines 2as shown in FIG. 1 are successively loaded to an antenna element 1.

with this formation,the inductive component of each transmission line 2is added in series to the impedance of the antenna element 1 which has alarge capacitive component. Further, the radiation current is superposedto the transmission lines 2.

FIGS. 3 and 4 are schematic diagrams of other embodiments of thisinvention. The embodiment shown in FIG. 3 has a plurality of foldedtransmission lines 3, while the one shown in FIG. 4 has curvedtransmission lines 4. I

Though dipole antennas are shown in the above embodiments, it will beunderstood that this invention is also applicable with similar effectsto monopole antennas as shown in FIG. 5. i

As described above, the antenna element is loaded with inductivecomponents of small loss and the antenna efficiency is not deteriorated.Further, as the radiation current is superposed to the loadingtransmission lines, the effective length of the antenna is equivalentlyincreased, the radiation resistance being thereby multiplied eight toten-fold. Thus, a small antenna with which the loss due to themismatching thereof with the receiver in the resonant state isminimized, is realized.

Further, according to this invention, broad-band characteristics equalto or even better than those of a normal mode helical antenna ofcorresponding length are achieved.

The chart of FIG. 6 shows impedance characteristics (A) for an antennaof this invention of 60 cm in length characteristics (B) for a helicalantenna of corresponding length.

Further, the antenna efficiency can be increased by changing the lengthorthe characteristic impedance of the loading transmission linesaccording to the respective loading positions, or by changing the spacesbetween adjacent transmission lines. Namely, as seen from thehereinbefore shown formula (1), impedance Z can be changed by varyingthe value of the characteristic impedance W, or the length l of theline. In the embodiment shown in FIG. 7, the lengths (l l of respectivetransmission lines are changed while the spaces (w) are equal. Theembodiment shown in FIG. 8 is loaded with transmission lines of the samelength (l) but differently spaced (w w On the other hand, FIG. 9 showsan embodiment in which the characteristic impedances (W W of the loadingtransmission lines are varied depending on the loading position alongThe antenna. In FIGS. 7 to 9, distance 2h represents the total length ofthe antenna.

It is important for the antenna of this invention to be provided in sucha form that simple construction, stable characteristics and easyhandling of the antenna are ensured. An example of such an antenna isdescribed hereunder.

Referring to FIGS. 10a, 10b and 100, a supporting cylinder 11 is made ofa dielectric material and provided with a hole 15 which serves as theoutlet for feeders. A conductive material in the pattern of antenna elements l3 loaded with short-circuited transmission lines 14 aredeposited, by known printed-circuit technique, on an elastic sheet 12 ofan insulating material. This elastic sheet 12 with the conductivepattern of the antenna deposited thereon is placed within the supportingcylinder 11 so that the sheet 12 is pressed against the inner wall ofthe cylinder 11 by its own elasticity. Thus, the sheet 22 is assuredlyheld by the cylinder 11 as shown in FIG. 100. Though a cylindrical tubeis used in the above embodiment, it will be understood that similareffects are achieved using a tube having a square section.

The antenna of this invention fabricated in such a form as describedabove has the following advantages. Namely, antennas of any complicatedpattern can be easily fabricated in mass-production scale with veryaccurate dimensions and good uniformness. Further, as the antennaelement is protected by the dielectric cylinder, it is little affectedby weather or salty wind and also hardly suffers mechanical damage.Thus, a long operation life can be expected. Moreover, the antennaassembly described is very simple in construction, as the printed sheetis certainly within the supporting cylinder with its own elasticity andno fixing means is required. Thus, the prduction cost is accordinglylow.

Another embodiment of this invention is shown in FIGS. 11 and 12. In theillustrated arrangement, the antenna according to this inventionconstitutes a part of a composite antenna, the other part being a rodantenna 24. The antenna 20 comprises support 21 which may be, forexample, a square bar of a dielectric material such as polys tyrole, anantenna element 23 which may be a series of conductive strips, forexample, of metal foil attached to the support 21 along a longitudinaledge thereof, and compensating elements 22 which are a plurality ofparallel two lines of conductor attached to the support 21, one end ofthe two lines being connected with the antenna element and the other endbeing short-circuited. The support 21 is provided with a hole along thelongitudinal axis thereof at the center portion of the square section.This hole serves to support the rod antenna 24 which operates at afrequency band different from that for the first antenna 20. Further, asboth antennas can be driven through a common feeding point, a compositeantenna of reduced size which may appear to be a single antenna isobtained. Moreover, the second or rod antenna 24 contributes to increasethe mechanical strength of the composite antenna.

What we claim is: a

1. An antenna means comprising two sets of linear conductors aligned ina plain dipole antenna fashion and having the total length substantiallyshorter than a half wavelength in the operation frequency band, thelinear conductors of each set of said two sets of linear conductorsbeing spaced at intervals corresponding to a fraction of the operatingwavelength,

a plurality of parallel two-wire type distributed constants transmissionlines having one end thereof short-circuited, said transmission linesbeing connected between two adjacent conductors of each set of said twosets of linear conductors at the other end of said transmission lines,said plurality of parallel two-wire type transmission lines beingperpendicular to the axis of said two sets of linear conductors andhaving a predetermined impedance characteristic,

a bar of dielectric material, said bar having on the surface thereofsaid two sets of linear conductorsand said plurality of paralleltwo-wire type distributed constants transmission lines, and

a rod of conductor along the longitudinal axis of said dielectric bar,said rod being designed to serve as another antenna which operates atanother frequency band, the feeding point for both antennas beingcommon, whereby said antenna means constitutes a part of a compositeantenna.

1. An antenna means comprising two sets of linear conductors aligned ina plain dipole antenna fashion and having the total length substantiallyshorter than a half wavelength in the operation frequency band, thelinear conductors of each set of said two sets of linear conductorsbeing spaced at intervals corresponding to a fraction of the operatingwavelength, a plurality of parallel two-wire type distributed constantstransmission lines having one end thereof short-circuited, saidtransmission lines being connected between two adjacent conductors ofeach set of said two sets of linear conductors at the other end of saidtransmission lines, said plurality of parallel two-wire typetransmission lines being perpendicular to the axis of said two sets oflinear conductors and having a predetermined impedance characteristic, abar of dielectric material, said bar having on the surface thereof saidtwo sets of linear conductors and said plurality of parallel two-wiretype distributed constants transmission lines, and a rod of conductoralong the longitudinal axis of said dielectric bar, said rod beingdesigned to serve as another antenna which operates at another frequencyband, the feeding point for both antennas being common, whereby saidantenna means constitutes a part of a composite antenna.